Standard Higgs Sector Research Articles

Generalized blind spots for dark matter direct detection in the 2HDM

In this paper we study the presence of generalized blind spots, i.e. regions of the parameter space where the spin-independent cross section for dark matter direct detection is suppressed, in the context of a generic 2HDM and a minimal fermionic Higgs-portal dark sector. To this end, we derive analytical expressions for the couplings of the dark matter to the light and heavy Higgses, and thus for the blind spot solutions. Unlike the case of a standard Higgs sector, blind spots can occur even without a cancellation between different contributions, while keeping unsuppressed and efficient the annihilation processes in the early Universe involving Higgs states. As a consequence, the allowed parameter space is dramatically enhanced.

Expectations for probing the Higgs–fermion and the Higgs–vector boson couplings at the ILC

Deviations from the standard Higgs sector generated by some new physics at an energy scale Λ could be described by an effective SU(3)c×SU(2)L×U(1) invariant non-renormalizable Lagrangian terms of dimension six. A systematic study of various Higgs boson production × decay channels (γγ, ZZ, WW, bb¯, ττ¯) at the International Linear Collider (ILC) in the SM extension by effective operators is carried out. Statistical methods are used to establish a degree of consistency for the standard Higgs sector with the forthcoming data, using the expected ILC accuracies of the Higgs boson production channels. Global fits in the two-parametric anomalous coupling space indicating possible deviations from the standard Higgs-fermion and Higgs-gauge boson couplings are performed.

Higgs boson signal at complete tree level in the SM extension by dimension-six operators

Deviations from the standard Higgs sector generated by some new (nonstandard) physics at an energy scale \Lambda could be described by an effective SU(3)_c x SU(2)_L x U(1) invariant non-renormalizable Lagrangian terms of dimension six. The set of dimension-six operators involving the Higgs field is chosen in such a way that the form of gauge bosons kinetic terms remains untouched, preserving all high-precision electroweak constraints. A systematic study of effects in various Higgs boson production channels (\gamma \gamma, ZZ, WW, bb-bar, \tau \tau-bar) caused by effecive operators is carried out beyond the {production x decay} approximation (or infinitely small width approximation). Statistical methods are used to establish consistency of the standard Higgs sector with the available LHC data. A global fit in the two-parametric anomalous coupling space indicating to possible deviations from the standard Higgs-fermion and Higgs-gauge boson couplings is performed, using post-Moriond 2012 data and more precise LC 2013 data. We find that the standard Higgs sector is consistent with the current CMS and ATLAS experimental results both in the infinitely small width approximantion and the calculation with complete gauge invariant sets of diagrams. However, visible difference of the exclusion contours is found for some combinations of production and decay channels, although minor for the global fits for all possible channels. Updates of the signal strength and the signal strength error reported at LC 2013 result in a significant improvements of the allowed regions in the anomalous coupling space, which are recalculated also at complete tree level.

Stückelberg axions and the effective action of anomalous Abelian models. A [formula omitted] model and its signature at the LHC

We elaborate on an extension of the Standard Model with a gauge structure enlarged by a single anomalous U ( 1 ) , where the presence of a Wess–Zumino term is motivated by the Green–Schwarz mechanism of string theory. The additional gauge interaction is anomalous and requires an axion for anomaly cancelation. The pseudoscalar implements the Stückelberg mechanism and undergoes mixing with the standard Higgs sector to render the additional U ( 1 ) massive. We consider a 2-Higgs doublet model. We show that the anomalous effective vertices involving neutral currents are potentially observable. We clarify their role in the case of simple processes such as Z ∗ → γ γ , which are at variance with respect to the Standard Model. A brief discussion of the implications of these studies for the LHC is included.